High-Performance Thin-Film Transistors of Quaternary Indium-Zinc-Tin Oxide Films Grown by Atomic Layer Deposition

In-Hwan Baek; Jung Joon Pyeon; Seong Ho Han; Ga-Yeon Lee; Byung Joon Choi; Jeong Hwan Han; Taek-Mo Chung; Cheol Seong Hwang; Seong Keun Kim

doi:10.1021/acsami.9b03331

High-Performance Thin-Film Transistors of Quaternary Indium-Zinc-Tin Oxide Films Grown by Atomic Layer Deposition

ACS Appl Mater Interfaces. 2019 Apr 24;11(16):14892-14901. doi: 10.1021/acsami.9b03331. Epub 2019 Apr 15.

Authors

In-Hwan Baek^{1

2}, Jung Joon Pyeon^{1

3}, Seong Ho Han⁴, Ga-Yeon Lee⁴, Byung Joon Choi⁵, Jeong Hwan Han⁵, Taek-Mo Chung⁴, Cheol Seong Hwang², Seong Keun Kim¹

Affiliations

¹ Center for Electronic Materials , Korea Institute of Science and Technology , Seoul 02792 , South Korea.
² Department of Materials Science and Engineering and Inter-University Semiconductor Research Center , Seoul National University , Seoul 08826 , South Korea.
³ KU-KIST Graduate School of Converging Science and Technology , Korea University , Seoul 02841 , South Korea.
⁴ Division of Advanced Materials , Korea Research Institute of Chemical Technology , Daejeon 34114 , South Korea.
⁵ Department of Materials Science and Engineering , Seoul National University of Science and Technology , Seoul 01811 , South Korea.

PMID: 30945837
DOI: 10.1021/acsami.9b03331

Abstract

A new deposition technique is required to grow the active oxide semiconductor layer for emerging oxide electronics beyond the conventional sputtering technique. Atomic layer deposition (ALD) has the benefits of versatile composition control, low defect density in films, and conformal growth over a complex structure, which can hardly be obtained with sputtering. This study demonstrates the feasibility of growing amorphous In-Zn-Sn-O (a-IZTO) through ALD for oxide thin-film transistor (TFT) applications. In the ALD of the a-IZTO film, the growth behavior indicates that there exists a growth correlation between the precursor molecules and the film surface where the ALD reaction occurs. This provides a detailed understanding of the ALD process that is required for precise composition control. The a-IZTO film with In/Zn/Sn = 10:70:20 was chosen for high-performance TFTs, among other compositions, regarding the field-effect mobility (μ_FE), turn-on voltage ( V_on), and subthreshold swing (SS) voltage. The optimized TFT device with the a-IZTO film thickness of 8 nm revealed a high performance with a μ_FE of 22 cm² V^-1 s^-1, V_on of 0.8 V, and SS of 0.15 V dec^-1 after annealing at 400 °C for 30 min. Furthermore, an emerging device such as a vertical channel TFT was demonstrated. Thus, the a-IZTO ALD process could offer promising opportunities for a variety of emerging oxide electronics beyond planar TFTs.

Keywords: In−Zn−Sn−O; amorphous oxide; atomic layer deposition; thin film transistor; vertical transistor.